Yosuke Aoki and others found a novel serine protease in erythroblast and granulocyte among myeloid cells and named the protease medullasin. They found that the function of medullasin is to activate NK cells and to cause inflammation (J. Biol. Chem. 253, 2026-2032 (1978); J. Clin. Invest. 69, 1223-1230 (1982)).
Moreover, Yosuke Aoki and others found and reported that medullasin also had the below described biological activities.
(1) Medullasin took part in controlling heme synthesis in an erythroblastand manifestation of pyridoxine reactive anemia.
(2) Medullasin took part in manifestation of anemia accompanied with chronic inflammation.
(3) Medullasin activity in a granulocyte increased when chronic inflammatory diseases became worse.
(4) When medullasin of physiological concentration was injected inside of an animal skin, an inflammation characterized by monocyte infiltration was caused and endothelial cells of fine vein were characteristically denatured.
(5) When human lymphocytes were treated with medullasin, their ability of DNA and RNA syntheses increased and their reactivity to various mitogens remarkably increased.
(6) When monocytes were treated with medullasin, their migration ability was obstructed whereas their superoxide productivity was increased.
(7) When granulocytes were treated with medullasin, their migration ability was increased.
(8) When human lymphocytes were treated with medullasin, their NK activity was remarkably increased but that was not through interferon production.
The total amino acid sequence of medullasin had not been determined, and only the supplier of medullasin was human bone marrow cell or human granulocyte. So the amount of medullasin available was limited.
The first purpose of the present invention is to clone the gene corresponding to medullasin by means of a genetic recombination method to clarify the sequence. It is thereby possible to clarify the gene coding medullasin or its precursor and at the same time to elucidate the amino acid sequence of the medullasin. The second purpose of the present invention is to enable us to synthesize medullasin by means of a chemical synthesis or a genetic recombination, and to obtain medullasin with high purity in large quantities.
Medullasin is contained in human myeloid cell or peripheral blood cells in large quantities. For example, about 10 .mu.g of medullasin was found in 1 ml of human peripheral blood. This medullasin is hardly found in other tissues and cells but is expressed specifically in human blood cells, especially only in leukocytes and erythroblasts.
Therefore, it is expected that to clarify the expression mechanism of the medullasin gene is to elucidate the gene expression specific to human leukocytes or erythroblasts which have not been clarified before.
In general, cell-specific gene expression is controlled by not only factors (trans factors) such as proteins being specific to the cells and so on, but also by the gene sequences existing around and in the chromosomal genes. Therefore, it is thought that a DNA sequence of a transcription controlling region, which is necessary for gene expression being specific to leukocytes and erythroblasts among human blood cells, exists around or in the chromosomal gene of the above described serine protease, medullasin derived from human myeloid cells.
Therefore, the third purpose of the present invention is to propose a DNA sequence of a transcription controlling region necessary for the cell-specific gene expression.